Rear 4-Link Bars & Components

What Is a 4-Link Rear Suspension?

A 4-link rear suspension locates the rear axle with four bars, two upper and two lower, that run from the housing to the chassis. The bars control how the axle moves under load, so the housing can't twist the way it can on leaf springs. That control reduces axle wrap and helps hold pinion angle when you launch hard.

Bar geometry sets the instant center, the imaginary point where lines drawn through the upper and lower bars meet. Moving the instant center changes anti-squat, which affects how the car plants the tires on launch. That's why many racers run brackets with multiple mounting holes.

A 4-link is one of several ways to locate a rear axle, and some builds use torque arms instead. You can browse other suspension components if you're still comparing layouts. Before you choose parts, read our 4-link suspension setup guide to see how bar angles and bracket positions work together.

Parallel vs. Triangulated 4-Link Suspension

The main difference is how each layout controls side-to-side axle movement. A parallel 4-link runs all four bars roughly parallel to the frame rails, so it needs a separate lateral locator. A triangulated 4-link angles the upper bars inward, which lets the bars handle lateral location on their own.

With a parallel setup, you'll add one of our Panhard bars and track bars to keep the axle centered under the car. Parallel layouts are common in drag cars because they leave room for wide tires and they're simple to adjust. The tradeoff is one more part to mount and set up.

A triangulated setup needs no Panhard bar, which saves space and parts. It's popular on street cars that see corners as well as straight lines. Because the upper bars sit at an angle, plan for clearance around the exhaust, fuel tank and floor pan.

4-Link Bars, Brackets and Components

You can buy a 4-link as a complete kit or build one piece by piece. Complete kits, like the Rhodes Race Cars Pro Series 4-Link Suspension Kit, bundle matched parts for you. For a custom setup, you'll shop these components separately:

• Upper and lower 4-link bars that connect the axle housing to the chassis
• Chassis brackets, such as the Competition Engineering Magnum Series bracket in 1/4"-thick hot-rolled steel
• Rear-end brackets that weld to the axle housing, sold in pairs by Competition Engineering
• Upper link brackets from Allstar Performance that weld to a 9" Ford housing
• Threaded tube ends that let you adjust each bar's length
• Matching rod ends and jam nuts that form the pivot at each end of a bar

Match every rod end to the thread size and direction of its tube end. Each bar typically uses a left-hand thread on one end and a right-hand thread on the other, so you can adjust length in place.

Bolt-On vs. Weld-On 4-Link Kits

Bolt-on kits install without welding, while weld-on kits require you to weld brackets to the chassis and axle housing. The right choice depends on your tools, your fabrication skills and how much you want to modify the car.

A bolt-on kit is designed for a specific vehicle. The RideTech Bolt-On 4-Link Rear Suspension System for 1967-1969 Chevy Camaro and Pontiac Firebird (GM F-Body) is one example. Heidts is another brand to check for complete 4-link kits. A bolt-on kit makes sense if you don't have welding equipment or want fewer permanent changes to the car.

Weld-on kits give you more control over bar placement and geometry. The RideTech 4Link Weld-On Rear Suspension Triangulated 4-Link Bars and Competition Engineering weld-on brackets suit custom chassis and race builds. Plan on precise measuring, since bracket position sets your instant center and pinion angle. If you're not an experienced fabricator, have a chassis shop handle the welding.

How to Choose 4-Link Tubing and Tube Ends

Choose tubing by outside diameter (OD) and wall thickness, then match the tube ends and rod ends to that size. Allstar Performance offers threaded tube end tubes in 5/8", 3/4", 1" and 1-1/4" OD, with wall thicknesses of .058", .065", .095" and .120". A thicker wall adds strength and weight, while a larger OD resists bending.

JEGS left- and right-hand threaded tube ends let you pair opposite threads on one bar, so turning the bar changes its length without disconnecting it. For 1-1/4" OD tubing, a QA1 weld-on wrench hex gives you a flat spot to hold the bar during adjustment. QuickCar Racing also offers a 5/8" x 7" suspension tube for shorter links.

Before you order, measure the center-to-center bar length you need. Then confirm your tube ends, rod ends and jam nuts share the same thread size. Once your measurements are set, shop the rear 4-link bars and components on this page to finish your build.